Method for bonding a nickel electrodeposit to a nickel surface



iatenied Dec. 21, 1948 METHOD FOR BONDING A NICKEL ELEC- TRODEPOSIT TO ANICKEL SURFACE Ralph Crysler McQuire, Port Colborne,.0ntario, Canada,assignor to The International Nickel Company, Inc., New York, N. Y., acorporation of Delaware No Drawing. Application February 26, 1946, Se-

rial No. 650,389. In Canada December 3, 1945 10 Claims.

The present invention relates to the treatment of a nickel startingsheet or other nickel surface in order to obtain adherence thereto of asubsequent nickel electro-plating and to the product obtained by suchtreatments.

The art has recognized the broad problem of securing satisfactoryvadherence or bonding between a nickel surface and a nickelelectroplating. Thus, U. S. Patent No. 2,001,385 discloses certainattempts which have been made in the art, such as the immersion of anickel starting sheet in a dilute acid solution without the addition ofother compounds thereto. An important feature of the process in the U.S. Patent No. 2,001,385 is immersion of the starting sheet in the diluteacid bath for several hours. Another U. S. patent, No. 2,299,054,discloses the anodic treatment of a nickel starting sheet in a sodiumcyanide solution to remove oxide film adhering thereto; the processdisclosed therein also involves a cathodic treatment in the same cyanidesolution prior to the electro-deposition of nickel. U. S. Patent No.2,299,054 discloses the application of an electric current foractivation of the nickel starting sheet. I amaware that other processeshave been proposed and attempted for the cleansing and activation ofother metal bases, for example, iron, prior to the electro-deposition ofa metal plating thereon. However, none of these proposals and attemptshas provided a satisfactory solution to the problem of securing anadequate bond between a nickel surface and a nickel electro-platlng.This will be readily recognized by reference to an article by Pinner,Soderberg and Baker in "Modern Efectroplating, 1942, page 237, in whichthe authors point out the difficulty in obtaining a good bond between aductile nickel coating and a relatively thin. brittle coating depositedfrom a high sulfate nickel bath.

In my ccpending applications U. S. Serial Numbers 635,774 and 635,775,both filed December 18, 1945, and entitled Method for bonding a nickelelectro-deposit to a nickel surface, I have disclosed processes forsecuring adequate bonding between a nickel surface and a nickelelectroplating. These processes involve the use of electric current andanodic treatment of the nickel surface. Furthermore, in myaforementioned copending applications, agitation is not an essentialfeature of the processes disclosed therein.

I have discovered a commercially feasible process for securing adequatebonding between a nickel surface and a nickel plating subsequentlyapplied thereto; my novel process is Well adapted to commercialproduction due to relatively short working time together with the factthat I do not utilize electric current in carrying out my novel process.

It is an object of the present invention to provide a process forsecuring adequate bonding between a nickel surface and a nickelelectroplating.

It is within the purview of the present invention to provide anelectro-deposited nickel cathode integral with and securely bonded to anickel starting sheet.

The present invention further aims to secure a high degree of economy byproviding for periodic recovery of certain of the reagents used in thebonding process.

The present invention further contemplates the provision of a pluralityof coherent bonded layers of electro-deposited nickel upon a metalarticle.

The scope of the present invention. likewise includes the removal of apassive film from a nickel surface prior to the electro-deposltion ofnickel thereon.

Various other objects, advantages and features of the present inventionwill become apparent from the following description:

Broadly speaking, the present invention involves the immersion of anickel surface in an aqueous acid chloride-bearing bath containing asignificant concentration of cupric ions. After the immersion treatment,the nickel surface is immediately immersed in a rinse tank containingwater and transferred to a nickel plating tank in which a nickel platingis deposited upon and securely bonded to the nickel surface. Thoseskilled in the art will realize that the expression nickel surface mayrefer to a nickel starting sheet, a prior' nickel plating, a cast ormachined nickel surface, or a wrought nickel surface. I

In practicing my invention, it is important that copper be preventedfrom depositing upon the nickel surface during the immersion treatment.Thus, I continuously pass compressed air through the solution while theimmersion process is being carried out. In this manner,

' the copper is maintained in the state of highest oxidation andprevented from depositing upon the nickel surface being treated. Hence.I secure economy of operation in that it is not necessary tocontinuously add copper salts to the solution except to replace drag-outlosses.

The composition of the bath employed for the immersion treatment of thenickel surface has an important effect upon the character of the bondobtained between the nickel-surface and the subsequently applied nickelplating. Thus, the acid chloride-bearing bath employed by the presentinvention contains at least about 9.0 grams of chloride ion per liter asI have found that the presence of chloride ions in the bath has a markedeffect on improving the bonding properties of the nickel surface treatedtherein. While a bath containing about 9.0 grams per liter of chlorideion has been found satisfactory: I prefer to employ a bath containingabout 30 to 36 grams per liter of chloride ion, as with the increasedchloride ion-- concentration of the bath, the time period required forsatisfactory immersion treatment of the nickel surface is decreased.Thus, I have found that satisfactory results are not obtained when abath substantially devoid of chloride ions and containing about 50 to200 grams per liter of sulfuric acid is employed. However, by addingchloride ions to the sulfuric acid bath, such as by adding 15 to 60grams per liter of sodium chloride, the bonding properties of a nickelsurface treated therein are markedly improved. It will, of course, beunderstood that an equivalent quantity of chloride ion can be added byemploying other suitable water soluble sources of chloride ions, such aspotassium chloride, magnesium chloride, hydrochloric acid, etc.Furthermore, satisfactory results are also obtained by employing anacidic bath that does not contain sulfate ion. Thus, for example, asolution containing about 50 to 200 grams per liter of hydrochloric acidgives satisfactory results for treating a nickel surface to which asecurely bonded nickel electrodeposit is subsequently applied.

. In accordance with the invention, about 0.5 to about 30 grams perliter of cupric ion in the form of any suitable water soluble source ofcopper ions is added to the acid bath employed, such as the bathshereinbefore described. However, the preferred range of cupric ionconcentration is from about 2 to about grams per liter. The presence ofthe requisite quantity of cupric ion is essential if proper bonding ofthe nickel surface to the subsequently applied nickel electrodeposit isto be obtained. In the absence -of cupric ion, the nickel surfaceremains relatively passive and the required activation of the surface isnot obtained. Consequently, satisfactory adherence of a subsequentnickel plating to the surface is not obtained.

For best results the treatment bath should be maintained at atemperature of about 60 F. to about 100? F. However, the temperature isnot critical and higher or lower temperatures may be utilized asdesired.

It is essential in carrying out the present invention to maintain thecopper in the bath in the cupric state during the immersion treatment ofthe nickel surface. Hence, the bath is agitated by blowing compressedair therethrough during the immersion treatment whereby the copper ismaintained in the state of highest oxidation. I have found that if suchagitation is not employed, copper deposits upon the nickel surface.However, it is within the scope of my invention to desired results. Anyfurther increase in chloride ion concentration of the bath does notsubstantially affect the time required for satisfactory treatment of thenickel surface.

Although a longer time period of treatment than hereinbefore describedmay be employed, I have found that a certain amount of nickel dissolvesin the bath during the immersion treatment, and accordingly, the time oftreatment should be kept as low as possible in order to decrease theamount of nickel dissolved. Entirely satisfactory results are obtainedas long as the nickel surface is immersed in the novel coppercontainingbath of the present invention for about 5 to 10 minutes as hereinbeforedescribed. The

advantages of activating the nickel surface in as short a period of timeas possible will be read-- ily apparent to those skilled in the art asit decreases to a large extent the number of tanks which must be madeavailable to carry out the treatment with resultant decrease in floorspace and investment charges.

After the immersion treatment is completed. the nickel surface isremoved from the bath andimmediately given a water rinse. After removalfrom the rinse tank, the treated nickel surface should be placed in anickel plating tank within about 60 minutes after removal from the rinsetank and nickel plated thereon. Otherwise, if the treated article isallowed to stand in air for more prolonged periods following treatment,a passive film will form on the nickel surface. In the event it is notdesired to apply the nickel plating shortly after the surface istreated, the nickel surface should be kept immersed in a bath which willprevent the formation of a passive film on the nickel surface. Thus, thenickel surface may be immersed in a bath of clean water until plating isto be begun: otherwise, satisfactory bonding of the treated nickelsurface to the electrodeposit of nickel is not obtained due to formationof a passive film on the treated nickel surface.

The following illustrative examples are provided in order that thoseskilled in the art may have a better understanding of the preferredmodes of practicing the invention.

Example I A nickel starting sheet was immersed in an acid bathcontaining about 100 grams per liter of sulfuric acid, about 50 gramsper liter of sodium chloride and about 5 grams per liter of cupric ionin the form of copper sulfate. immersion was continued for about 5minutes at a temperature of about 80 F., with agitation of the bath bypassing compressed air therethrough. After the treatment was completed,the starting sheet was removed from the acid bath and im-- mersed in awater rinse tank. From the rinse tank, the starting sheet wastransferred to a nickel plating tank and nickel plated thereon until adeposit about 0.25 inch thick was obtained The Example I! An ironarticle having a nickel plating thereon was treated in an acid bathcontaining about 60 grams per liter of hydrochloric acid and about gramsper liter of cuprlc ion in the form of cupric chloride. The immersionwas continued for about 5 minutes at a temperature of about 80F. withagitation of the bath by passing compressed air therethrough. After thetreatment was completed, the article was removed from the acid bath andplaced in a rinse tank. After the water rinse, the article was immersedin a conventional Watts type nickel plating solution and a seconddeposit oi nickel plated thereon. It was observed that the second nickelplating had substantially no tendency to strip or peel from the firstnickel electro-plating, and entirely satisfactory bonding between thetwo nickel platings was obtained.

Although. various concentration ranges for the reagents used in my novelprocess have been set forth in the foregoing description, it is to beunderstood that the invention is not to be limited to these'specificranges, particularly with regard to hydrochloric acid, sulfuric acid andchloride ion concentrations. Thus, for example, the preferred loweramount of hydrochloric acid concentration set forth for an all-chloridebath is about 50 grams per liter. As hereinbefore stated, satisfactoryresults are obtained by employing the present invention when a chlorideion concentration lower than that equivalent to 50 grams per liter ofhydrochloric acid is employed, for ex ample, a bath containing at leastabout 9 grams per'liter of chloride ion. However, baths having aconcentration higher than about 9 grams per liter of chloride ion arepreferred, as the increased chlorlde ion concentration allows forsatisfactory treatment of the nickel surface in a shorter time. Althoughan upper amount of 200 grams per liter of hydrochloric acid hashereinbefore been shown to give satisfactory results, this concentrationof hydrochloric acid was chosen for economic reasons, as greaterconcentrations can be employed without departing from the spirit andscope of the invention. Similarly,

' the concentration of sulfuric acid in the chloridebearing treatmentbath may be varied from the range of 50 to 200 grams per literhereinbefore shown; the stated range of 50 to 200-grams per liter ofsulfuric acid in a bath containing at least about 9.0 grams per liter ofchloride ion having been found to provide satisfactory treatment ofnickel surfaces to'which a nickel electro-plating is subsequentlyapplied. 1

Although thepresent invention has been desheet for about 5 minuteswithout the application of electric current from an external source inan aqueous bath containing about 100 grams'per liter of sulfuric acid,about .50 grams per liter 'of sodium chloride and about 5 gramsper'liter of copper in the form of copper sulfate and the balanceessentially water, maintaining said copper in the cupric state bypassing air through said bath, removing said nickel starting sheet fromsaid aqueous bath, rinsing said starting sheet with water, immersingsaid starting sheet in a nickel electro-plating bath and eiectroscribedin conjunction with certain preferred em- ,bodiments, it is to beunderstood that modifications and variations may be resorted to with-.1

out departing from the spirit and scope of the invention as thoseskilled in the art will readily depositing nickel on said nickelstarting sheet.

2. A method for obtaining improved bonding" of a nickel electro-depositto a nickel surface which comprises immersing a metal article having anickel plating thereon for about 5 minutes without the application ofelectric current from an external source in an aqueous bath containingabout grams per lit :r of hydrochloric acid, about 5 grams per liter ofcopper as cupric chloride and the balance essentially water, maintainingsaid copper in the cupric state by passing air through said bath,removing said metal article from said aqueous bath,'rinsing said metalarticle with water, immersing said metal article in a nickelelectro-plating bath and electro-depositing nickel on the nickel surfaceof said metal article.

3. A method for obtaining improved bonding of a nickel electro-depositto a nickel surface which comprises immersing an article having a nickelsurface for about 5 to is minutes without the application of electriccurrent from an external source in an aqueous bath containing about 50to 200 grams per liter of sulfuric acid, about l5 to about 60 grams perliter of sodium chloride, copper sulfate in an amount to provide about0.5 to 30 grams per liter of copper as cupric ion and the balanceessentially water, passing air through said bath during immersion ofsaid article, removing said article from said bath, rinsing'saidarticle, immersing said article in a nickel electro-plating bath andelectro-depositing nickel on the nickel surface of said article.

4. A method for obtaining improved bonding of a nickel electro-depositto a nickel surface which comprises immersing an article having a nickelsurface for about 5 tom m nutes without the application of electriccurrent from an external source in an aqueous bath containing about 50to about 200 grams per liter of hydrochloric acid, about 0.5 to 30 gramsper liter of copper as cupric chloride and the balance essentiallywater, passing air through said bath during immersion of said article,removing said article from said aqueous bath, rinsing said article,immersing said article in a nickel electro-plating bath andelectro-depositing nickel on the nickel surface of said article. l

5. A method for obtaining improved bonding of a nickel electrodeposit toa nickel surface which the application of electric current from anexternal source in an'aqueous acid bath containing about 50 to about 200grams per liter of sulfuric acid; a chloride compound from the'groupconsisting of hydrochloric acid, sodium chloride,- potassium chlorideandmagnesium chloride to tially water; passing air through said bathduring immersion of said article; removing said article from said bath;rinsing said article; immersing said article in a nickel electroplatingbath and electrodepositing nickel on the nickel surface'of said article.

6. A methodfor obtaining improved bonding of a nickel electrodeposit toa nickel surface which comprises immersing an article having a nickelsurface for about to about minutes without the application of electriccurrent from an external source in an aqueous acid bath containing about50 to about 200 grams per liter of sulfuric acid; a chloride compoundfrom the group consisting of hydrochloric acid, sodium'chloride, po-

tassium chloride and magnesium chloride to provide a chloride ionconcentration of about 9 to about 36 grams per liter; a water-solublecopper compound to provide a cupric ion concentration of about 0.5 toabout 30 grams per liter and the balance essentially water; passing airthrough said bath, during immersion of said, article; removing saidarticle from said bath; rinsing said article; immersing said article ina nickel electroplating bath and electrodepositing nickel on the nickelsurface of said article.

'7. A method for obtaining improved bonding of a nickel electrodepositto a nickel surface which comprises immersing an article having a nickelsurface for about 5 to about 10 minutes without the application ofelectric current from an external source in an aqueous acid bathcontaining about 50 to about 200 grams per liter of sulfuric acid; achloride compound from the group consisting of hydrochloric acid, sodiumchloride, potassium chloride and magnesium chloride to pro vide achloride ion concentration of about 9 to about 36 grams per liter; awater-soluble source of cupric ions from the group consisting of coppersulfate and cupric chloride to provide a cupric ion concentration ofabout 0.5 to about 30 grams per liter and the balance essentially water;passing air through said bath during immersion of said article; removingsaid article from said bath; rinsing said article; immersing saidarticle in a nickel electroplating bath and electrodepositing nickel onthe nickel surface of said article.

8. A method for obtaining improved bonding of a nickel electrodeposit toan article having a nickel surface which comprises establishin anaqueous acid bath containing at least about 9 grams per liter ofchloride ion provided by one member selected from the group consistingof hydrochloric acid in an amount up to about 200 gramsper liter, sodiumchloride up to an amount correspondingto about 36 grams per liter ofchloride ion, potassium chloride up to an amount corresponding to about36 grams per liter of chloride ion and magnesium chloride up to anamount corresponding to about 36 grams per liter ofchloride ion; acidfrom the group consisting of sulfuric acid and hydrochloric'acid toprovide a total acid content in said bath of about 50 to about 200 gramsper liter; 2. copper compound from the group consisting of coppersulfate and cupric chloride to provide a cupric ion concentration insaid bath of about 0.5 to about 30 grams per liter and the balanceconsisting essentially of water;

immersing said article having said nickel surface in said bath for about5 to about 10 minutes without the application of electric current froman external source to activate said nickel surface of said article;passing air through said bath during immersion of said article tooxidize cuprous ions to cupric ions; removing said article from saidbath; rinsing said article to remove adhering bath solution from theactivated nickel surface of said article; transferring said article to anickel electroplating bath; and electrodepositing nickel on theactivated nickel surface of said article whereby an improved bonding ofa nickel electrodeposit to the activated nickel surface of said articleis obtained.

9. A method for obtaining improved bondingof a nickel electrodeposit toan article having a nickel surface which comprises establishing anaqueous acid bath containing at least about 9 grams per liter ofchloride ion provided by one member selected from the group consistingof hydrochloric acid in an amount up to about 200 grams per liter,sodium chloride up to an amount correspending to about 36 grams perliter of chloride ion, potassium chloride up to an amount correspondingto about 36 grams per liter of chloride ion and magnesium chloride up toan amount corresponding to about 36 grams per liter of chloride ion;acid from the group consisting of sulfuric acid and hydrochloric acid toprovide a total acid content in said bath of about to about 200 gramsper liter; a copper compound fromthe group consisting of copper sulfateand cupric chloride to provide a cupric ion concentration in said bathof about 2 to about 10 grams per liter and the balance consistingessentially of water; immersing said article having said nickel surfacein said bath for about 5 to about 10 minutes without the application ofelectric current from an external source to activate said nickel'surface of said article; passing air through said cuprous ions tocupric ions; removing said article from said bath; rinsing said articleto remove adhering bath solution from the activated nickeL surface ofsaid article; transferring said article to a nickel electroplating bath;and electrodepositing nickel on the activated nickel surface of saidarticle whereby an improved bonding of a nickel electrodeposit to theactivated nickel surface of said article is obtained.

10. A method for obtaining improved bonding of a nickel electrodepositto an article having a nickel surface which comprises establishing anaqueous acid bath containing at least about 9 grams per liter ofchloride ion provided by one member selected from the group consistingof hydrochloric acid in an amount up to about 200 grams per liter,sodium chloride up to an amount corresponding to about 36 grams perliter of chloride ion, potassium chloride up to an amount correspondingto about 36 grams per liter of chloride ion and magnesium chloride up toan amount corresponding to about 36 grams per liter of chloride ion acidfrom the group consisting of sulfuric acid and hydrochloric acid toprovide a total acid content in said bath of about 50 to about 200 gramsper liter; a copper compound from the group consisting of copper sulfateand cupric chloride to provide a cupric ion concentration in said bathof about 0.5 to about 30 grams per liter and the balance consistingessentially of water; immersing said article having said nickel surfacein said bath for about 5 to about 10 minutes without the application ofelectric current from an external source to activate said nickel surfaceof said article; passing air through said bath during immersion of saidarticle to oxidize cuprous ions to cupric ions; remov-- ing said articlefrom said bath; immersing said trodepositing nickel on the activatednickel sur- I face of said article whereby an improved bonding of anickel electrodeposit to the activated nickel surface of said article isobtained.

RALPH CRYSLER. McQUIREL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 765,371 Aylsworth July 19, 19041,373,837 Schulte Apr. 5, 1921 OTHER REFERENCES Iron Age, Sept. 26,1940, pages 19, 20; Oct. 3, 1940, pages 32, 33.

